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Photo ID: h32i57Subject: VolcanoesDescription
Active Volcanoes; Cascade Range; EDM; Eruptions; Geologic Hazards; Intrustions; Stratovolcanoes; Theodolite; Uplifts; Volcanic Features; Volcanism; VolcanologyGeologists use a theodolite and an Electronic Distance Meter to measure angles and slope-distances to the Mt. St. Helens lava dome. Changes in these angles and distances are used to calculate 'deformation rates'. The rates often reached as much as 30 feet per hour as magma rose and the dome expanded before extrusion started.
Lyn Topinka

Credit Line: Courtesy USGS Cascade Volcano Observatory
North America; United States; Washington; Mount Saint Helens
Photo Quality | Large 

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